Sol-gel pre-treatments and coatings are an important class of passive
protective coatings, which can effectively prevent corrosion of various
metallic substrates through adhesion improvement and barrier protection.
Recently, sol-gel chemistry has been proposed as an appropriate method
for implementation of self-healing functionality in coatings via extrinsic
concepts. In this review we will analyze the most relevant existing works
on self-healing sol-gel coatings, including new work done in the direction of
implementing intrinsic healing capabilities to sol-gels. The development of
active sol-gel coatings is due to the broad chemical versatility of precursors
and low processing temperature of this type of chemistry.